Which is faster?

[[deleted]]

A simple question this time.

Which procedure is faster:
1. a sql query with 2 or 3 joins on 3 tables each 500.000 records.
2. 3 seperate select sql queries (without joins) on 3 tables each 500.000 records.

The returned resultset is in case 1: 50 row, and in case 2: 20 rows for each query.

Best regards, Twan

[jweissig]

hi,

i would have to say #1 but you should really test this out.. create a script and time the 2 differient ways. I also suggest making an index of the three table.. look on google for more info.

• Justin

[[deleted]]

Thanks for the help! 🙂

[simonsky]

I would say #2 if you have simple query like where X=Y

Joining 3 tables is a lot slower than joining 2 tables, it's not trible the time of a single query, but "cube" the time, i.e. if t= single query's time. time for joining 3 tables = approx. ttt.

Of course the real situation is a lot more complicated than the above simpy math. and it always depends on how effcient your database design is.

Simonsky

[ultraslacker]

If you are joining at all intelligently and if you are using a dbms with a competent planner, than use joins. Not only will the query be faster (test it and see), but your overhead will be less!